Submission #942395

#	Time	Username	Problem	Language	Result	Execution time	Memory
942395		THXuan	Race (IOI11_race)	C++14	0 / 100	35 ms	88664 KiB

race

#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <queue>
#include <set>
#include <map>
#define INF 1e18
using namespace std;
typedef long long ll;

int n, k;
ll ans = INF;
vector<pair<int ,int>>adj[200005];
bool visited[200005];
ll dp[200005], cnt[10000000];
vector<ll>v;

int get_size(int s, int e) {
	dp[s] = 1;
	for (auto u : adj[s]) {
		if (u.first == e || visited[u.first]) continue;
		get_size(u.first, s);
		dp[s] += dp[u.first];
	}
	return dp[s];
}

int get_centroid(int s, int e, int n) {
	for (auto u : adj[s]) {
		if (u.first == e || visited[u.first]) continue;
		if (dp[u.first] * 2 > n)return get_centroid(u.first, s, n);
	}
	return s;
}

void dfs(int s, int e, bool flag, int sum, ll dep = 2) {
	if (sum > k) return;
	if (!flag) {
		ans = min(ans, dep + cnt[k - sum]);
	}
	else {
		cnt[sum] = min(cnt[sum], dep);
		v.push_back(sum);
	}
	for (auto u : adj[s]) {
		if (u.first == e || visited[u.first]) continue;
		dfs(u.first, s, flag, sum + u.second, dep + 1);
	}
}

void centroid_decomposition(int node) {
	int centroid = get_centroid(node, 0, get_size(node, 0));
	visited[centroid] = true;
	for (auto u : adj[centroid]) {
		if (!visited[u.first]) {
			if (u.second <= k)ans = min(ans, 1 + cnt[k - u.second]);
			dfs(u.first, centroid, false, u.second);
			cnt[u.second] = min(cnt[u.second], 1*1ll);
			v.push_back(u.second);
			dfs(u.first, centroid, true, u.second);
		}
	}
	for (auto u : v) cnt[u] = INF;
	v.clear();
	for (auto u : adj[centroid]) {
		if (!visited[u.first])centroid_decomposition(u.first);
	}
}

int best_path(int n, int k, int h[][2], int l[]) {
	for (int i = 0; i <= 10000000; i++) cnt[i] = INF;
	for (int i = 1; i <= n - 1; i++) {
		adj[h[i][0]].push_back({ h[i][1], l[i] });
		adj[h[i][1]].push_back({ h[i][0],l[i]});
	}
	centroid_decomposition(1);
	if (ans == INF) return -1;
	return ans;
}

Compilation message (stderr)

race.cpp: In function 'int best_path(int, int, int (*)[2], int*)':
race.cpp:72:45: warning: iteration 10000000 invokes undefined behavior [-Waggressive-loop-optimizations]
   72 |  for (int i = 0; i <= 10000000; i++) cnt[i] = INF;
      |                                             ^
race.cpp:72:20: note: within this loop
   72 |  for (int i = 0; i <= 10000000; i++) cnt[i] = INF;
      |                  ~~^~~~~~~~~~~

• Subtask 1: 0 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57